Fix namespace rule runtime crash - #499

Coverage increased (+0.002%) to 97.667% when pulling 69a1dec on wKich:commonjs-namespace into 90dedd7 on benmosher:master.

Coverage increased (+0.004%) to 97.669% when pulling 8171db3 on wKich:commonjs-namespace into 90dedd7 on benmosher:master.

this fixes #416, yeah? or did you find and fix independently?

also: thanks! 😄 can you add a changelog note?

@benmosher, sure. I found it while working in my own project.

Coverage increased (+0.004%) to 97.669% when pulling bbeb404 on wKich:commonjs-namespace into 90dedd7 on benmosher:master.